/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.classfile.util;

import proguard.classfile.*;
import proguard.classfile.visitor.*;

import java.util.*;

/**
 * This ClassVisitor links all corresponding non-private, non-static, non-initializer methods in the class hierarchies
 * of all visited classes. Visited classes are typically all class files that are not being subclassed. Chains of links
 * that have been created in previous invocations are merged with new chains of links, in order to create a consistent
 * set of chains.
 *
 * @author Eric Lafortune
 */
public class MethodLinker extends SimplifiedVisitor implements ClassVisitor, MemberVisitor {
    // An object that is reset and reused every time.
    // The map: [class member name+' '+descriptor - class member info]
    private final Map memberMap = new HashMap();

    // Implementations for ClassVisitor.

    public void visitAnyClass(Clazz clazz) {
        // Collect all non-private members in this class hierarchy.
        clazz.hierarchyAccept(true, true, true, false, new AllMethodVisitor(
            new MemberAccessFilter(0, ClassConstants.ACC_PRIVATE | ClassConstants.ACC_STATIC, this)));

        // Clean up for the next class hierarchy.
        memberMap.clear();
    }

    // Implementations for MemberVisitor.

    public void visitAnyMember(Clazz clazz, Member member) {
        // Get the class member's name and descriptor.
        String name = member.getName(clazz);
        String descriptor = member.getDescriptor(clazz);

        // Special cases: <clinit> and <init> are always kept unchanged.
        // We can ignore them here.
        if (ClassUtil.isInitializer(name)) {
            return;
        }

        // See if we've already come across a method with the same name and
        // descriptor.
        String key = name + ' ' + descriptor;
        Member otherMember = (Member)memberMap.get(key);

        if (otherMember == null) {
            // Get the last method in the chain.
            Member thisLastMember = lastMember(member);

            // Store the new class method in the map.
            memberMap.put(key, thisLastMember);
        } else {
            // Link both members.
            link(member, otherMember);
        }
    }

    // Small utility methods.

    /**
     * Links the two given class members.
     */
    private static void link(Member member1, Member member2) {
        // Get the last methods in the both chains.
        Member lastMember1 = lastMember(member1);
        Member lastMember2 = lastMember(member2);

        // Check if both link chains aren't already ending in the same element.
        if (!lastMember1.equals(lastMember2)) {
            // Merge the two chains, with the library members last.
            if (lastMember2 instanceof LibraryMember) {
                lastMember1.setVisitorInfo(lastMember2);
            } else {
                lastMember2.setVisitorInfo(lastMember1);
            }
        }
    }

    /**
     * Finds the last class member in the linked list of related class members.
     * 
     * @param member the given class member.
     * @return the last class member in the linked list.
     */
    public static Member lastMember(Member member) {
        Member lastMember = member;
        while (lastMember.getVisitorInfo() != null && lastMember.getVisitorInfo() instanceof Member) {
            lastMember = (Member)lastMember.getVisitorInfo();
        }

        return lastMember;
    }

    /**
     * Finds the last visitor accepter in the linked list of visitors.
     * 
     * @param visitorAccepter the given method.
     * @return the last method in the linked list.
     */
    public static VisitorAccepter lastVisitorAccepter(VisitorAccepter visitorAccepter) {
        VisitorAccepter lastVisitorAccepter = visitorAccepter;
        while (lastVisitorAccepter.getVisitorInfo() != null
            && lastVisitorAccepter.getVisitorInfo() instanceof VisitorAccepter) {
            lastVisitorAccepter = (VisitorAccepter)lastVisitorAccepter.getVisitorInfo();
        }

        return lastVisitorAccepter;
    }
}
